https://wccftech.com/xbox-backward-compatibility-debuts-with-16-titles-on-xcloud-for-game-pass-ultimate-users/

Xbox backward compatibility has often been touted as one of the main advantages Microsoft was able to build over Sony. Having practically the entire Xbox library at one's disposal, including the games made for the original Xbox, is certainly a feature much appreciated by a lot of gamers.

Starting today, however, Microsoft is extending Xbox backward compatibility for Game Pass Ultimate subscribers to xCloud. This means you'll get to play the following sixteen titles on your smartphone or tablet, and the library should grow soon.